KINETICS OF THE SIH3 + O2 REACTION STUDIED BY TIME-RESOLVED MASS-SPECTROMETRY

The SiH3 + O2 reaction was studied by means of time-resolved mass spectrometric detection of SiH3 with a near-threshold electron impact ionization technique. The rate constant of (1.26 +/- 0.18) x 10(-11) cm3 molecule-1 s-1 at T = 293 K was determined from the first-order decay rates of SiH3 produced in ArF (193 nm) laser photolysis of CCl4/SiH4/O2/He or N2O/SiH4/O2/He mixtures. The signal at m/z 47 attributable to SiH3O could be detected as a direct product of the SiH3 + O2 reaction. On the basis of kinetic simulations, the branching ratio for the reaction of SiH3 + O2 --> HSiOOH + H was determined to be 0.6 +/- 0.1. Branching ratios for the other two channels, SiH3 + O2 --> SiH3O + O and SiH2O + OH, were estimated to be 0.16 and 0.24, respectively.